Direct Click Bonding of Dissimilar Solid Materials Based on the Catalyst-Free Huisgen 1,3-Dipolar Cycloaddition.

Here, "direct click bonding" of solid materials is proposed, which is the direct bonding of solid surfaces via the formation of covalent bonds without any adhesive. The present study shows that the Cu-free Huisgen 1,3-dipolar cycloaddition reaction proceeds between solid surfaces displaying cyclooctyne and azide groups, and it achieved the strong bonding of dissimilar solid materials as a macroscopic reaction. The bonding strength obtained is sufficiently high for practical use, and the strength can be controlled by the surface density of the cyclooctyne groups. The click bonding reaction proceeds at ambient temperature in water, an organic solvent, air, and vacuum without a catalyst or a byproduct. The bonding strength is kept more than 2 years. The click bonding works for different types of substrate materials as long as alkyne and azide groups are displayed on their surfaces. The X-ray photoelectron spectroscopy (XPS) measurements provide an evidence that the Cu-free Huisgen 1,3-dipolar cycloaddition reaction proceeds between the solid surfaces through the click bonding.